Many human diseases, such as Huntington's, Parkinson's, and Alzheimer's, and normal physiological states, such as aging, are strongly influenced by exposure to environmental stress. However, little is known about the mechanisms by which environmental stressors are detected and discriminated from one another in animals. The long term objective of this work is to utilize functional genomic approaches in the nematode C. elegans to define fundamental environmental stress sensing and signaling mechanisms. Such studies will more precisely define the role of the environment in human health and disease and help to define the modes of action of numerous toxic substances. The specific hypothesis to be tested in this proposal is that compartment specific protein damage constitutes a feedback inhibition mechanism for discrimination between different forms of environmental stress. This hypothesis is based on the observations that 1) knockdown of protein homeostasis (PH) genes that normally prevent the accumulation of some forms of protein damage activates osmosensitive gene expression 2) Knockdown of PH genes that activate osmosensitive gene expression accelerates protein aggregation 3) Protein damage induced by heat and oxidative stress does not activate osmosensitive gene expression. The specific aims of this proposal are: 1) Define the PH genes that are transcriptionally regulated by environmental stressors. We will examine the spatial and temporal, and functional involvement of PH genes in response to environmental stress using i) comparative whole genome microarray analysis of heat, oxidative, and osmotically induced gene expression in wild type and transcription factor mutant animals ii) in vivo localization of GFP tagged PH genes during exposure to environmental stress iii) stress survival assays in transgenic animals overexpressing PH targets. 2) Test the role of protein misfolding as an activator of stress induced gene expression. Protein damage will be genetically induced using RNAi knockdown of specific PH complexes. The effects of each gene knockdown on the activation of heat, oxidative, and osmotic stress signaling pathways will be quantified by i) in vivo high throughput fluorescence measurements of animals expressing stress-specific GFP reporters ii) epistasis analysis using stress sensing transcription factor mutants iii) whole animal survival assays in PH knockdown animals.